Integral slope adjusting and jacking process method for multi-link small box girder with simple support and continuous oblique crossing in sequence

Abstract

The invention discloses an integral slope adjusting and jacking process method for a multi-link small box girder simply supported first and then continuously obliquely crossed. The method comprises the following steps: firstly, dismantling bridge protection facilities and drainage systems of a first link and a second link of a right part; excavating earthwork at a bridge abutment and a bridge pier, pouring a cushion layer, constructing a counter-force foundation bracket and a counter-force embracing column beam bearing platform, and arranging a jacking support system at the top of the counter-force foundation bracket and the counter-force embracing column beam bearing platform; limiting devices are installed at the ends of the bridge abutments and the tops of the fourth pier and the eighth pier; the main beams and the cover beams of the first unit and the second unit are jacked; the pier is subjected to height addition construction, and a bridge abutment is transformed into a pier structure; padstones at the top of a cover beam are chiseled away, a reinforcing mesh is arranged, concrete is poured, the beam is dropped synchronously after the strength reaches the standard, and bridge deck pavement and auxiliary engineering are constructed after support padstones are replaced. The steps are repeated to conduct jacking construction on the bridge left part; and finally, jacking equipment materials are dismantled, and the field is removed. Through the combination of synchronous jacking and slope adjusting jacking technologies, intelligent monitoring is achieved, the construction efficiency is improved, and the construction period is shortened.

Description

Technical Field

[0001] This invention belongs to the field of bridge reconstruction technology, and more specifically, relates to a method for adjusting the slope and lifting the jacking of a multi-span, initially simply supported, then continuous skewed small box girder. Background Technology

[0002] In the process of continuous improvement and upgrading of highway transportation networks, the rapid increase in traffic flow and the continuous improvement of road grades have created an urgent need for the renovation and upgrading of a large number of existing bridges. To adapt to new traffic standards, these bridges often require jacking to adjust their slope. Bridge jacking technology, with its unique advantages, has gradually become an effective means in the field of bridge renovation. This technology, by rationally setting up a temporary support system at the bottom of the bridge and using equipment such as jacks to lift the bridge, can achieve a series of renovation construction operations such as pier heightening and bearing replacement.

[0003] However, the jacking construction of multi-span, initially simply supported, then continuous skew-girder bridges presents even more complex challenges. Due to their skewed nature, skew-girder structures exhibit extremely complex stress characteristics. During jacking, the girder is prone to torsion and lateral displacement, placing extremely high demands on jacking accuracy and stability control. Furthermore, the jacking construction of multi-span bridges requires careful consideration of the mutual influence between the bridge spans, necessitating precise coordination of operations at multiple jacking points. Deviation at any jacking point can affect the overall construction quality and safety of the bridge. Existing bridge jacking technologies are insufficient to fully meet the construction requirements of such specialized structures. They either fail to adequately address the torsion and lateral displacement issues of skew-girder bridges or lack the precision necessary to coordinate the operations at each jacking point in multi-span bridges, leading to low construction efficiency and increased safety risks. Summary of the Invention

[0004] To address the aforementioned deficiencies or improvement needs of existing technologies, this invention provides a method for the overall slope adjustment and jacking of multi-section, initially simply supported, then continuously skewed small box girders. By setting reaction foundation corbels at the abutments and reaction column-supporting beams at the piers, a stable support foundation is provided for the bridge jacking construction. This ensures that the bridge is evenly stressed during the jacking process, avoiding structural deformation or damage caused by uneven local stress, and ensuring the safety and reliability of the construction process. Furthermore, installing sliding PTFE plates between the jacks and steel pipe columns at the fourth pier eliminates structural internal force changes caused by temperature differences, ensuring the long-term stability and durability of the bridge under different environmental conditions. During the process, comprehensive longitudinal and lateral limiting devices were installed to effectively restrict the horizontal displacement of the bridge during jacking, preventing beam torsion and lateral offset. Simultaneously, a dual force control system (force + stroke) was employed to monitor the pressure and displacement of the jacks in real time. A PLC hydraulic control system enabled precise control of multiple jacking points. Synchronous jacking ensured that all parts within the bridge section rose to the same height. Slope-adjustable jacking achieved linear proportional jacking based on the designed longitudinal slope data, with the jacking speed set proportionally to ensure the bridge accurately reached the designed slope. Furthermore, during jacking, the position and verticality of the jacks could be adjusted promptly based on the beam's rotation, improving jacking accuracy.

[0005] To achieve the above objectives, the present invention provides a method for adjusting the slope and lifting the overall jacking of a multi-section, initially simply supported, then continuous, oblique small box girder, comprising the following steps: S100: First, remove the bridge crash barriers, pedestrian guardrails, expansion joints, and bridge drainage system of the first and second sections on the right side. S200: Excavate the earthwork at the abutment and the first to eighth piers, pour the foundation layer, construct the reaction foundation corbel at the abutment and the reaction column-holding beam cap at the first to eighth piers, and install the first jacking support system on the top of the reaction foundation corbel, and the second and third jacking support systems on the top of the reaction column-holding beam cap. S300: Install a first lateral limiting device at the end of the bridge abutment, and install several first longitudinal limiting devices on the top of the bridge deck of the fourth and eighth piers. S400: Lift the main beams and cap beams of the first and second sections respectively; S500: The first to eighth piers will be extended and the abutments will be converted into pier structures. S600: Remove the existing pad stone on the top of the cap beam, retain the pad stone reinforcement and arrange the steel mesh according to the drawing, erect the formwork and pour the concrete. After the concrete strength reaches the standard, the beam is lowered simultaneously. After all the bearing pad stones are replaced, the bridge deck paving and ancillary works can be constructed. S700: Repeat steps S100 to S600 to carry out jacking construction on the left side of the bridge; S800: Lifting equipment materials dismantling and removal from the site.

[0006] Furthermore, in step S200, when constructing the reaction foundation corbel at the bridge abutment, mechanical excavation is first carried out on both sides of the cross section, followed by layered slope excavation of the area under the bridge, and formwork is erected according to the design dimensions of the reaction foundation corbel. The interface between the new and old concrete is roughened, then steel bars are inserted into the abutment pier, and steel bars are tied in the formwork according to the design requirements. Finally, the reaction foundation corbel is poured. When constructing the reaction column caps at the first to eighth piers, the foundation was excavated in layers with slope according to the design dimensions of the reaction column caps, formwork was erected, the interface between the old and new concrete was roughened, steel bars were inserted into the pier columns, and steel bars were tied in the formwork according to the design before the reaction column caps were poured.

[0007] Further, in step S200, the first lifting support system includes a first steel pipe column, a first transverse connecting rod, a first inclined connecting rod, a first jack, and a first steel distribution beam. Multiple first steel pipe columns are fixedly installed on the top of each reaction foundation bracket by bolts. The multiple first steel pipe columns are distributed in a triangular pattern. Multiple first transverse connecting rods and first inclined connecting rods are spaced apart between every two first steel pipe columns. Four inverted first jacks are provided on the top of the first steel pipe columns. A first steel distribution beam is fixedly installed on the top of the four inverted first jacks by bolts. The first steel distribution beam is located at the bottom of the main beam. The second jacking support system is installed on the top of the reaction column beam cap of the first to seventh piers. It includes a second steel pipe column, a second transverse connecting rod, a second inclined connecting rod, a second jack, a third jack, and a second steel distribution beam. Multiple second steel pipe columns are fixedly installed on the top of each reaction foundation corbel by bolts. The multiple second steel pipe columns are symmetrically arranged in the transverse and longitudinal directions of the pier. Multiple second transverse connecting rods and second inclined connecting rods are spaced apart between every two first steel pipe columns. Four second jacks are installed on the top of the second steel pipe columns at the bottom of the cap beam. The second jacks are located at the bottom of the cap beam. An inverted third jack is installed on the top of the second steel pipe columns on each side of the pier cap beam. A second steel distribution beam is fixedly installed on the top of the inverted third jack by bolts. The second steel distribution beam is located at the bottom of the main beam. The third jacking support system includes a third steel pipe column, a third transverse connecting rod, a third oblique connecting rod, a fourth jack, a fifth jack, and a third steel distribution beam. Multiple third steel pipe columns are bolted to the top of each reaction foundation corbel. Multiple second steel pipe columns are symmetrically arranged along the longitudinal direction of the pier. Multiple third transverse connecting rods and third oblique connecting rods are spaced apart between every two first steel pipe columns. Four fourth jacks are installed on the top of the third steel pipe columns at the bottom of the cap beam. An inverted fifth jack is installed on the top of the second steel pipe column on the left side of the cap beam of the eighth pier. A third steel distribution beam is bolted to the top of the inverted fifth jack and is located at the bottom of the main beam.

[0008] Further, in step S300, the first lateral limiting device adopts a frame-type lateral limiting device, which includes multiple fourth steel pipe columns, fourth lateral connecting rods, fourth oblique connecting rods and first sliding rods. The fourth steel pipe columns are fixed to the top of the bridge abutment foundation by bolts. Multiple fourth lateral connecting rods and fourth oblique connecting rods are fixedly installed at intervals between the multiple fourth steel pipe columns. A first sliding rod is slidably connected to each fourth steel pipe column. The first sliding rod is fixedly connected to the bridge deck, and a stabilizing rod is fixedly installed between the first sliding rods. The first longitudinal limiting device is a boat-shaped longitudinal limiting device, which includes a reaction frame, a tie plate, a transverse diaphragm, a screw jack, a pad, and a reaction plate. The reaction frame is fixedly installed between the ends of the tie plate, the transverse diaphragm is fixedly installed between the middle parts, and the reaction plate is fixedly installed between the other ends. The pad is fixedly installed on the inward side of the reaction plate, and a screw jack is provided between the pad and the transverse diaphragm. The first longitudinal limiting device is fixedly connected to the bridge deck at the expansion joint of the fourth pier and the eighth pier respectively through the transverse diaphragm and the reaction frame, thereby limiting the longitudinal displacement of the bridge.

[0009] Furthermore, step S400 specifically includes the following steps: S410: Lift the first section of the bridge as a whole to ensure that all parts within the section rise synchronously. At the same time, carry out slope adjustment and lifting operations for the second section. By precisely controlling the height difference of each lifting point, the bridge section can achieve the slope required by the design. S420: According to the cutting positions determined by the construction drawings, the first to seventh piers are cut. After the cutting is completed, the cap beam is lifted. The cap beam is lifted steadily to the predetermined height by gradually lifting with jacks. S430: The first section of the bridge is jacked up to adjust the slope. By precisely controlling the height difference of each jacking point, the section of the bridge reaches the slope required by the design. The cap beam is then jacked up synchronously, so that the cap beam rises smoothly to the predetermined height. S440: Remove the first longitudinal limiting device at the eighth pier, then remove the third span of the bridge, and install a second lateral limiting device at the end of the second span to limit the lateral displacement of the bridge. Install a second longitudinal limiting device between the left and right spans of the bridge deck at the sixth pier. S450: Lift the first and second spans of the bridge as a whole to the design elevation; S460: Install a sliding PTFE plate between the steel pipe support and the jack at the fourth pier. After installation, remove the first span of the abutment.

[0010] Furthermore, when jacking the first and second sections of the bridge, an alternating cyclic jacking method using two sets of jacks is adopted. While one set of jacks is depressurized, the other set of jacks is already under support. The jacking process is as follows: Before the formal jacking, a trial jacking should be carried out. The trial jacking height is 10mm. The working performance of the jacks and temporary support system and the stability of the box girder are checked during and after the jacking process. The cap beam can only be jacked after the pier columns are cut according to the design requirements. The jacking speed is controlled at 1-3mm / min. The weight of the jacking section structure is calculated by using the jacking pressure and jack parameters and compared with the design weight. After the trial jacking is completed, if there are no problems, the formal jacking will begin. Each jacking stroke is 100mm, and the maximum jacking speed is 3mm / min. The jacking support system is synchronously controlled by the PLC hydraulic control system to achieve synchronous slope adjustment and jacking of the bridge. During the jacking process, the jacks are shimmed in stages. The jacks are first shimmed with 1cm steel plates according to the jacking height, and then replaced with 0.1m, 0.2m, 0.5m, 1m, and 2m steel supports in sequence. The longitudinal and transverse connecting rods are immediately added to enhance the stability of the support.

[0011] Further, in step S440, the second lateral limiting device adopts a frame-type lateral limiting device, which includes multiple fifth steel pipe columns, fifth lateral connecting rods, fifth oblique connecting rods, and second sliding rods. The fifth steel pipe columns are fixed to the top of the reaction force column-supporting beam bearing platform by bolts. Multiple fifth lateral connecting rods and fifth oblique connecting rods are fixedly installed at intervals between the multiple fifth steel pipe columns. A second sliding rod is slidably connected to each fifth steel pipe column. The second sliding rod is fixedly connected to the bridge deck, and a stabilizing rod is fixedly installed between the second sliding rods. The second longitudinal limiting device includes a sixth steel pipe column and a third sliding rod. The sixth steel pipe column is fixedly installed on the right bridge deck with bolts, and its bottom is leveled with mortar. Multiple transverse and diagonal connecting rods are installed between the sixth steel pipe columns. Before installing the third sliding rod, the pavement layer in the installation area of ​​the second longitudinal limiting device needs to be removed. One end of the third sliding rod is slidably connected to the sixth steel pipe column, and the other end is installed on the beam with anchor bolts. Multiple transverse and diagonal connecting rods are fixedly installed between the two third sliding rods. During the installation process, care should be taken to avoid the top plate steel strands to prevent unnecessary impact on the structure.

[0012] Furthermore, in step S500, when constructing the extension of the bridge pier, the main steps include: Concrete removal: Before extending the column, remove 30cm of old pier concrete from the upper and lower surfaces of the pier column to form a "convex" joint surface and a 6mm rough surface, exposing the main reinforcement. After cleaning, use a cutting machine to trim the edge of the column to ensure that the edge is straight. Reinforcing bar processing and connection: Reinforcing bar processing is completed in the processing plant and inspected and accepted after being transported to the site. The main bars are mechanically connected, and the joint standard is Grade I. They are staggered. Within the joint section, the hoops are spot welded to the main bars. When binding the reinforcing cage, ensure that the grade, diameter, number and spacing of the reinforcing bars meet the design requirements. The bound or welded reinforcing mesh and reinforcing cage shall not be deformed, loose or unwelded. Steel formwork installation: After the steel formwork is processed off-site, it is transported to the construction site. When assembling the formwork, double-sided tape is used at the joints to prevent grout leakage. After assembly, the joints are cleaned and water-based release agent is applied. After the formwork is installed, guy ropes are used to secure it. The plane position and verticality of the formwork are re-measured to ensure installation accuracy. The top of the formwork is higher than the top surface of the connecting column, and hoppers are symmetrically opened to facilitate concrete pouring and vibration. Concrete pouring: Before pouring concrete, check the formwork, reinforcement and protective layer. Use self-compacting C40 concrete and pour it in one go. Use a wall-mounted vibrator to compact the concrete to ensure it is dense. The top surface is constructed from the gap between the pier top and the beam bottom. When the concrete strength reaches 50% of the design strength, the formwork can be removed. After demolding, wrap it with plastic film for curing for no less than 7 days.

[0013] Furthermore, before the bridge is jacked up, elevation observation points are set up on the bridge deck, settlement monitoring points are set up on the reaction column beam abutment, vertical displacement monitoring points are set up on the main beam and cap beam, longitudinal displacement monitoring points are set up at the expansion joint, stress monitoring points are set up on the main beam, steel pipe column and cap beam, and temperature monitoring points are set up on the main beam.

[0014] Furthermore, during the jacking process, wedge-shaped steel plates are inserted between the steel distribution beam and the jacks to adjust the verticality of the jacks. With the help of the bolt return holes, the jacks can move back and forth in the direction of the bridge, thereby eliminating deviations and avoiding the influence of beam rotation.

[0015] In summary, compared with the prior art, the above-described technical solutions conceived by this invention can achieve the following beneficial effects: 1. The continuous skewed small box girder integral slope adjustment and jacking process of the present invention significantly reduces the reconstruction cost and shortens the construction period. Compared with demolition and reconstruction, this process does not require large-scale demolition of the main bridge structure, reducing the generation of construction waste and the consumption of building materials, and significantly reducing project costs. At the same time, by combining synchronous jacking and slope adjustment jacking technologies, and applying intelligent monitoring and control technologies, construction efficiency is improved and the construction period is shortened.

[0016] 2. The continuous skewed small box girder integral slope adjustment and jacking process of the present invention provides a stable support foundation for bridge jacking construction by setting reaction foundation corbels at the abutments and reaction column-holding beam caps at the piers. This significantly enhances the integrity and stability of the bridge, allowing it to be evenly stressed during the jacking process and avoiding structural deformation or damage caused by uneven local stress. This ensures the safety and reliability of the construction process. Furthermore, by installing sliding PTFE plates between the jacks and steel pipe columns at the fourth pier, the impact of diurnal temperature differences on the stability of the bridge structure is effectively solved. Temperature differences can cause thermal expansion and contraction of the bridge beams, resulting in additional stress and displacement on the lower support structure. The sliding PTFE plates allow the beams to slide freely under the influence of temperature differences, eliminating changes in internal forces caused by temperature variations and ensuring the long-term stability and durability of the bridge under different environmental conditions.

[0017] 3. The continuous skewed small box girder integral slope adjustment and jacking process of the present invention incorporates comprehensive longitudinal and lateral limiting devices during construction. These devices effectively restrict potential horizontal displacement of the bridge during jacking, preventing girder torsion and lateral offset, and ensuring the overall stability of the bridge structure during the jacking process. Furthermore, a force + stroke dual force control system is employed to monitor the pressure and displacement of the jacks in real time. If the error exceeds the set value, the system automatically shuts off the hydraulic valves to prevent damage to the bridge structure due to uneven force or excessive displacement deviation, thus ensuring the safety of the construction process.

[0018] 4. The continuous skewed small box girder integral slope adjustment and jacking process of the present invention achieves precise control of multiple jacking points through a PLC hydraulic control system. Synchronous jacking ensures that all parts within the span rise to the same height. Slope adjustment jacking can achieve linear proportional jacking based on the design longitudinal slope data, and the jacking speed is set proportionally, ensuring that the bridge can accurately reach the design slope requirements. Simultaneously, during the jacking process, the position and verticality of the jacks can be adjusted in a timely manner according to the rotation of the girder, improving jacking accuracy. Attached Figure Description

[0019] Figure 1 This is a schematic flowchart of the overall slope adjustment and jacking process for the skewed small box girder according to an embodiment of the present invention; Figure 2 This is a schematic diagram of step S100 of the overall slope adjustment and jacking process method for skewed small box girders according to an embodiment of the present invention; Figure 3 This is a schematic diagram of step S200 of the overall slope adjustment and jacking process method for skewed small box girders according to an embodiment of the present invention; Figure 4 This is a schematic diagram of step S300 of the overall slope adjustment and jacking process method for skewed small box girders according to an embodiment of the present invention; Figure 5 This is a schematic diagram of step S400 of the overall slope adjustment and jacking process method for skewed small box girders according to an embodiment of the present invention; Figure 6 This is a schematic diagram of step S500 of the overall slope adjustment and jacking process method for skewed small box girders according to an embodiment of the present invention; Figure 7 This is a schematic diagram of step S600 of the overall slope adjustment and jacking process method for skewed small box girders according to an embodiment of the present invention; Figure 8 This is an elevation view of the first lifting support system of the overall slope adjustment and lifting process method for skewed small box girders according to an embodiment of the present invention; Figure 9 This is a plan view of the first lifting support system of the overall slope adjustment and lifting process of the skewed small box girder according to an embodiment of the present invention; Figure 10 This is an elevation view of the second lifting support system of the overall slope adjustment and lifting process for skewed small box girders according to an embodiment of the present invention; Figure 11 This is a plan view of the second lifting support system of the overall slope adjustment and lifting process for skewed small box girders according to an embodiment of the present invention; Figure 12 This is an elevation view of the third lifting support system in the overall slope adjustment and lifting process of the skewed small box girder according to an embodiment of the present invention; Figure 13 This is a plan view of the third lifting support system in the overall slope adjustment and lifting process of the skewed small box girder according to an embodiment of the present invention; Figure 14This is an elevation view of the first lateral limiting device in the overall slope adjustment and jacking process of the skewed small box girder according to an embodiment of the present invention; Figure 15 This is a plan view of the first lateral limiting device in the overall slope adjustment and jacking process of the skewed small box girder according to an embodiment of the present invention; Figure 16 This is an elevation view of the first longitudinal limiting device in the overall slope adjustment and jacking process of the skewed small box girder according to an embodiment of the present invention; Figure 17 This is a plan view of the first longitudinal limiting device in the overall slope adjustment and jacking process of the skewed small box girder according to an embodiment of the present invention; Figure 18 This is an elevation view of the second lateral limiting device in the overall slope adjustment and jacking process of the skewed small box girder according to an embodiment of the present invention; Figure 19 This is a side view of the second lateral limiting device in the overall slope adjustment and lifting process of the skewed small box girder according to an embodiment of the present invention; Figure 20 This is an elevation view of the second longitudinal limiting device in the overall slope adjustment and jacking process of the skewed small box girder according to an embodiment of the present invention; Figure 21 This is a top view of the second longitudinal limiting device in the overall slope adjustment and jacking process of the oblique small box girder according to an embodiment of the present invention.

[0020] In all the accompanying drawings, the same reference numerals denote the same technical features, specifically: 1-Abutment, 2-First Pier, 3-Second Pier, 4-Third Pier, 5-Fourth Pier, 6-Fifth Pier, 7-Sixth Pier, 8-Seventh Pier, 9-Eighth Pier, 10-First Lifting Support System, 1001-First Steel Pipe Column, 1002-First Transverse Connecting Rod, 1003-First Diagonal Connecting Rod, 1004-First Jack, 1005-First Steel Distribution Beam, 11-Second Lifting Support System, 1101-Second Steel Pipe Column, 1102-Second Transverse Connecting Rod, 1103-Second Diagonal Connecting Rod, 1104-Second Jack, 1105-Third Jack, 1106-Second Steel Distribution Beam, 12-Third Lifting Support System, 1201-Third Steel Pipe Column, 1202-Third... 10203 - Third oblique connecting rod, 1204 - Fourth jack, 1205 - Fifth jack, 1206 - Third steel distribution beam, 13 - First lateral limiting device, 1301 - Fourth steel pipe column, 1302 - Fourth lateral connecting rod, 1303 - Fourth oblique connecting rod, 1304 - First sliding rod, 14 - First longitudinal limiting device, 1401 - Reaction frame, 1402 - Pull plate, 1403 - Horizontal partition plate, 1404 - Spiral jack, 1405 - Pad, 1406 - Reaction plate, 15 - Second lateral limiting device, 1501 - Fifth steel pipe column, 1502 - Fifth lateral connecting rod, 1503 - Fifth oblique connecting rod, 1504 - Second sliding rod, 16 - Second longitudinal limiting device, 1601 - Sixth steel pipe column, 1602 - Third sliding rod. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0022] Example 1 Combination Figure 1-5 ,like Figure 6 As shown, this invention provides a method for adjusting the slope and lifting the overall structure of a multi-section, initially simply supported, then continuously skewed small box girder, comprising the following steps: S100: First, remove the bridge crash barriers, pedestrian guardrails, expansion joints, and bridge drainage system of the first and second sections on the right side. Furthermore, to facilitate the installation of the limiting devices, the entire bridge deck pavement layer will be milled within the installation range of both the longitudinal and lateral limiting devices. The milling depth must reach the top surface of the bridge structure to ensure that the limiting devices can be securely installed on the bridge structure, thus providing a stable support foundation for subsequent jacking and support construction. During the milling process, the milling depth must be strictly controlled to avoid unnecessary damage to the bridge structure. Milling waste should be cleaned up promptly to maintain a clean construction site.

[0023] S200: Excavate the earthwork at abutment 1 and piers 2-9 from the first to the eighth, pour the foundation layer, construct the reaction foundation corbel at abutment 1 and the reaction column-holding beam cap at piers 2-9 from the first to the eighth, and install a first jacking support system 10 on the top of the reaction foundation corbel, and install a second jacking support system 11 and a third jacking support system 12 on the top of the reaction column-holding beam cap; Specifically, during the construction of the reaction foundation corbel at abutment 1, mechanical excavation was first carried out on both sides of the cross-section, followed by layered slope excavation of the area under the bridge. Formwork was erected according to the design dimensions of the reaction foundation corbel, and the interface between the old and new concrete was roughened. Next, reinforcing bars were inserted into the abutment pier of abutment 1, and the reinforcing bars were tied in the formwork according to design requirements. Finally, the concrete for the reaction foundation corbel was poured.

[0024] When constructing the reaction column abutments at locations 2-9 of the first to eighth piers, the foundation was excavated in layers with a slope according to the design dimensions of the reaction column abutments. Formwork was erected, and the interface between the old and new concrete was roughened. Reinforcing bars were inserted into the pier columns and tied inside the formwork according to the design requirements. Then, the concrete for the reaction column abutments was poured.

[0025] Furthermore, the top surface of the reaction column base must not exceed the original ground level. If it does, the reaction column base should be moved down, and the spacing of the lower edge reinforcement bars should be adjusted according to the bottom dimensions.

[0026] Furthermore, the first lifting support system 10 includes a first steel pipe column 1001, a first transverse connecting rod 1002, a first inclined connecting rod 1003, a first jack 1004, and a first steel distribution beam 1005. Each reaction foundation bracket has multiple first steel pipe columns 1001 fixedly installed on its top by bolts. The multiple first steel pipe columns 1001 are distributed in a triangular pattern. Multiple first transverse connecting rods 1002 and first inclined connecting rods 1003 are spaced apart between every two first steel pipe columns 1001. The top of the first steel pipe column 1001 is provided with four inverted first jacks 1004. The top of the four inverted first jacks 1004 is fixedly installed with a first steel distribution beam 1005 by bolts. The first steel distribution beam 1005 is located at the bottom of the main beam. The second jacking support system 11 is installed on the top of the reaction column-supporting beam abutment of the first to seventh piers (2-8). It includes a second steel pipe column 1101, a second transverse connecting rod 1102, a second inclined connecting rod 1103, a second jack 1104, a third jack 1105, and a second steel distribution beam 1106. Multiple second steel pipe columns 1101 are bolted to the top of each reaction foundation corbel. The multiple second steel pipe columns 1101 are symmetrically arranged in the transverse and longitudinal directions of the pier. Every two first steel pipe columns Multiple second transverse connecting rods 1102 and second oblique connecting rods 1103 are spaced apart between 1101. Four second jacks 1104 are installed on the top of the second steel pipe column 1101 at the bottom of the cap beam. The second jacks 1104 are located at the bottom of the cap beam. An inverted third jack 1105 is installed on the top of the second steel pipe column 1101 on each side of the pier cap beam. A second steel distribution beam 1106 is fixedly installed on the top of the inverted third jack 1105 by bolts. The second steel distribution beam 1106 is located at the bottom of the main beam.

[0027] The third jacking support system 12 includes a third steel pipe column 1201, a third transverse connecting rod 1202, a third inclined connecting rod 1203, a fourth jack 1204, a fifth jack 1205, and a third steel distribution beam 1206. Multiple third steel pipe columns 1201 are bolted to the top of each reaction foundation corbel. Multiple second steel pipe columns 1201 are symmetrically arranged along the longitudinal direction of the bridge pier. Multiple third transverse connecting rods are spaced apart between every two first steel pipe columns 1201. Connecting rod 1202 and third inclined connecting rod 1203, four fourth jacks 1204 are installed on the top of the third steel pipe column 1201 at the bottom of the cap beam. The fourth jacks 1204 are located at the bottom of the cap beam. An inverted fifth jack 1205 is installed on the top of the second steel pipe column 1201 on the left side of the cap beam of the eighth pier 9. The top of the inverted fifth jack 1205 is fixed with a third steel distribution beam 1206 by bolts. The third steel distribution beam 1206 is located at the bottom of the main beam.

[0028] The steel distribution beam adopts a box structure with dimensions of 600mm×1000mm. It is made of Q235C steel plates with thicknesses of 10mm, 20mm, and 40mm respectively, and internal stiffening plates are welded to enhance structural stability.

[0029] Furthermore, concrete spacers are required between the top of the steel distribution beam and the small box girder for leveling the bottom of the beam. The spacers are connected to the bottom of the beam using rebar anchoring and reinforced with a steel mesh. When pouring the concrete spacers, the bottom formwork directly utilizes the distribution beam, while side formwork for the spacers is installed on the outside, with grouting holes at the top and bottom of the side formwork. After the lower steel distribution beam is installed to the design elevation, the spacers are grouted using C60 non-shrink grout in conjunction with grouting equipment.

[0030] Specifically, the prefabricated steel distribution beams are transported to the site and then lifted by a truck crane to a position directly beneath the bridge. A steel wire rope is then laid across the bridge deck, with lifting lugs installed at both ends. The length of the lugs is adjusted according to the actual height on site. A hand-operated hoist is attached to the lifting point, and the distribution beam is slowly lifted until it reaches the bottom elevation of the leveling pads before installation. Necessary limiting measures must be taken on the bridge deck to limit the steel wire ropes and prevent slippage during lifting, which could lead to installation deviations. A trial lift must be conducted before installation to ensure that all related facilities are stable and secure.

[0031] The steel pipe columns are equipped with flanges at both ends, and stiffening plates are welded at the joints between the flanges and the steel pipes. Around each pier, except for the first 2-meter steel pipe column, the remaining steel pipe columns are arranged in a ring with a horizontal connecting rod every 1 meter. The upper and lower horizontal connecting rods are intersected by diagonal connecting rods, thus connecting all the steel pipe columns of a single pier into a whole.

[0032] Furthermore, the dimensions of the steel pipe columns include 0.1m, 0.2m, 0.5m, 1m, and 2m. The 0.1m and 0.2m steel pipe columns serve as temporary steel pads to accommodate the jacking stroke. A dedicated conversion joint is used for conversion between the two. All steel supports are connected by bolts pre-installed on the flanges at both ends to ensure overall stability. During the jacking operation, after each 1m jacking distance, the previously supported steel pipe columns must be replaced with 1m or 0.5m steel pipe columns, and flange plates must be installed at both ends of the replaced steel supports. Simultaneously, a horizontal connecting rod is installed at the flange plate at the bottom of the steel pipe column to ensure that the free end of the support does not exceed 1.5m.

[0033] S300: A first lateral limiting device 13 is installed at the end of the bridge abutment 1, and several first longitudinal limiting devices 14 are installed on the top of the bridge deck of the fourth pier 5 and the eighth pier 9. Due to adverse factors such as vertical errors in jack installation and changes in the horizontal length of the box girder during the jacking process, horizontal displacement may occur during the jacking process. To avoid such situations, longitudinal and transverse limiting devices need to be installed during the bridge jacking process to limit possible longitudinal and transverse displacement.

[0034] Furthermore, the first lateral limiting device 13 adopts a frame-type lateral limiting, which includes multiple fourth steel pipe columns 1301, fourth lateral connecting rods 1302, fourth oblique connecting rods 1303, and first sliding rods 1304. The fourth steel pipe columns 1301 are fixed to the top of the bridge abutment by bolts. Multiple fourth lateral connecting rods 1302 and fourth oblique connecting rods 1303 are fixedly installed at intervals between the multiple fourth steel pipe columns 1301. A first sliding rod 1304 is slidably connected to each fourth steel pipe column 1301. The first sliding rod 1304 is fixedly connected to the bridge deck, and a stabilizing rod is fixedly installed between the first sliding rods 1304.

[0035] The first longitudinal limiting device 14 is a boat-shaped longitudinal limiting device, which includes a reaction frame 1401, a pull plate 1402, a transverse diaphragm 1403, a screw jack 1404, a pad block 1405, and a reaction plate 1406. The reaction frame 1402 is fixedly installed between the ends of the pull plate 1402, the transverse diaphragm 1403 is fixedly installed between the middle parts, and the reaction plate 1406 is fixedly installed between the other ends. The pad block 1405 is fixedly installed on the inward side of the reaction plate 1406. The screw jack 1404 is provided between the pad block 1405 and the transverse diaphragm 1403. The first longitudinal limiting device 14 is fixedly connected to the bridge deck at the expansion joint of the fourth pier and the eighth pier through the transverse diaphragm 1403 and the reaction frame 1401, respectively, to limit the longitudinal displacement of the bridge.

[0036] Specifically, during the jacking process, the bridge girder will elongate longitudinally due to rotation, thereby generating a longitudinal horizontal force on the steel pipe columns. To ensure structural safety, several first longitudinal limiting devices 14 need to be installed along the transverse direction at the expansion joint between the fourth and eighth piers to longitudinally secure each span of the jacking box girder and prevent column slippage or vertical rotation under the action of horizontal force. Simultaneously, the screw jacks equipped on each first longitudinal limiting device 14 can be used to adjust the gaps at the girder ends.

[0037] S400: Lift the main beams and cap beams of the first and second sections respectively; The PLC synchronous jacking system employs a single control system to manage nine alternating jacking pump stations. One four-point alternating synchronous pump station is positioned for each pier, with each station placed at the corresponding pier location. All nine pump stations per span are connected to a main control unit via signal lines. The main control unit can perform two operations by outputting displacement commands: first, outputting a uniform displacement command to complete synchronous overall jacking; second, outputting different displacement commands for each pier to achieve proportional synchronous slope adjustment jacking. The jacking operation stops immediately after the displacement sensors transmit the specified displacement data back to the main control unit.

[0038] The two sets of jacks are connected at different points on the same pumping station. Each point has two interfaces, an oil inlet and an oil return, which are connected to the corresponding oil inlet and return lines of the jack cylinders, respectively. The pumping station controls the jack cylinders to lift the beam and lower it by retracting the cylinders.

[0039] During the lifting process, the computer uses the actual lifting displacement collected by the installed displacement sensors as a reference to compare and adjust it with the commanded displacement. If the actual displacement is greater than the commanded displacement, the pump station is controlled to reduce the pump oil pressure of the jacks at that location, slowing down the actual displacement until it matches the commanded displacement. If the actual displacement is less than the commanded displacement, the pressure is increased to accelerate the actual displacement, ensuring that the actual displacement of each group remains synchronized with the commanded displacement during lifting. Simultaneously, the system monitors the pressure of each group. If the pressure exceeds the warning value or an abnormality occurs, the equipment operating status must be checked immediately, or the lifting speed adjusted appropriately to ensure precise mutual control of the lifting pressure and lifting displacement.

[0040] Specifically, when jacking the first and second sections of the bridge, an alternating cyclic jacking method using two sets of jacks is adopted. While one set of jacks is depressurized, the other set of jacks is already under support. In the event of a sudden jack failure, the safety of the superstructure is effectively guaranteed, and the jacked bridge structure can achieve the desired lifting, slope change, descent, and correction according to the expected procedure. During the alternating jacking process, the bridge beam is supported alternately by two sets of jacks. When the two sets of jacks are in alternating support, the beam displacement remains controllable. Under each support setting, the compression of the support system remains almost constant, and therefore the internal forces within the beam also remain almost unchanged. Simultaneously, as one set of jacks releases pressure, the other set begins extending its cylinders to lift the beam, eliminating the height difference between support points. Under this operating method, the beam displacement is continuously controlled from the start to the end of the jacking process. The pressure of each jack is also continuously monitored, thus ensuring that the beam is not damaged during the jacking process, and the entire support system, including the beam, is under monitoring. Therefore, the entire bridge jacking system is in a safe and controllable state.

[0041] The jacking process is as follows: Before the formal jacking, a trial jacking should be carried out. The trial jacking height is 10mm. The working performance of the jacks and temporary support system and the stability of the box girder are checked during and after the jacking process. The cap beam can only be jacked after the pier columns are cut according to the design requirements. The jacking speed is controlled at 1-3mm / min. The weight of the jacking section structure is calculated by using the jacking pressure and jack parameters and compared with the design weight. After the trial jacking is completed, if there are no problems, the formal jacking will begin. Each jacking stroke is 100mm, and the maximum jacking speed is 3mm / min. The jacking support system is synchronously controlled by the PLC hydraulic control system to achieve synchronous slope adjustment and jacking of the bridge. During the jacking process, the jacks are shimmed in stages. The jacks are first shimmed with 1cm steel plates according to the jacking height, and then replaced with 0.1m, 0.2m, 0.5m, 1m, and 2m steel supports in sequence. The longitudinal and transverse connecting rods are immediately added to enhance the stability of the support.

[0042] The jacking control primarily employs a dual force control system: force and stroke. "Force" refers to the pressure sensor controlling the hydraulic pressure of the jacks, located above the hydraulic valves and connected to the computer control panel for real-time display. If the pressure error exceeds 5%, the control system immediately and automatically shuts off the hydraulic valves to ensure the safety of the jacking and the superstructure. "Stroke" refers to the displacement sensor controlling the jack stroke. The displacement should remain synchronized throughout the jacking process. This sensor is also connected to the computer control panel for real-time display. If the displacement error exceeds 1mm, the control system immediately and automatically shuts off the hydraulic valves to ensure the safety of the jacking and the superstructure. Precise positioning of each displacement sensor is required before jacking.

[0043] Furthermore, the first and second sections are lifted synchronously and slope-adjusted, respectively. Synchronous lifting means that all jacks under each section of the bridge are lifted to the same height. Slope-adjusted lifting is based on the design longitudinal slope data, with all jacks under each section of the bridge lifting in a linear proportional manner, and the lifting speed is set according to the proportion of the lifting height. The lifting is divided into multi-stage lifting, with each stage of lifting controlled equally according to the total lifting amount, and the lifting speed of each pier is set based on the stage lifting amount.

[0044] During the jacking process, as the longitudinal slope is adjusted, the projected length of the beam will gradually increase, which may cause the jack center to deviate from the support center. In this case, the jacks need to be adjusted to realign with the support center. When the beam rotates, the jacks will rotate accordingly, requiring the addition of wedge blocks at the tail of the jacks for leveling. The bolts connecting the steel distribution beam and the jacks are adjustable vertically. Inserting wedge steel plates between them ensures that the verticality of the jacks is controlled within 5‰. Typically, the wedge steel plates need to be adjusted every five strokes. Using the bolt's return hole, the jacks can move back and forth along the bridge direction, thereby eliminating deviations and avoiding the influence of beam rotation.

[0045] Furthermore, step S400 specifically includes the following steps: S410: Simultaneously lift the first section of the bridge to ensure that all parts within the section rise to the same height. At the same time, carry out slope adjustment and lifting operations for the second section. By precisely controlling the height difference of each lifting point, the bridge section can achieve the slope required by the design. Specifically, during the bridge jacking operation, a synchronous jacking operation must be implemented for the first span of the bridge. During the operation, the operational status of each jacking point must be strictly controlled to ensure that all parts within the span can rise smoothly to the same height, thereby guaranteeing the stability and stress balance of the overall structure of the first span of the bridge.

[0046] For the second section of the bridge, slope adjustment and jacking operations are required. This process necessitates the use of a high-precision monitoring and control system to precisely adjust the height differences between each jacking point. By differentially controlling the lift at different jacking points, the second section of the bridge can gradually reach the designed slope, meeting the functional requirements and safety standards for subsequent use.

[0047] S420: According to the cutting positions determined by the construction drawings, the first to seventh piers are cut. After the cutting is completed, the cap beam is lifted. The cap beam is lifted steadily to the predetermined height by gradually lifting with jacks. Furthermore, before cutting the pier, the jacks under the cap beam are controlled by the main unit and inflated to 80% of their own load capacity. At this point, the hydraulic locks of each jack are locked, and the sensors and other monitoring equipment are all in normal working condition. After tightening the mechanical screws to secure the top cap, the pier can be cut sequentially.

[0048] For the cutting operations of the first to seventh piers, a new type of vibration-free linear cutting equipment will be used to cut the columns. The cutting line will be set 0.3m above the column beam, while ensuring that the cutting height of the equipment is consistent with the height of the column cutting surface.

[0049] S430: The first section of the bridge is jacked up to adjust the slope. By precisely controlling the height difference of each jacking point, the section of the bridge reaches the slope required by the design. The cap beam is then jacked up synchronously, so that the cap beam rises smoothly to the predetermined height. During the bridge jacking operation, a slope adjustment jacking operation is required for the first span of the bridge. During the operation, a high-precision monitoring and control system is used to precisely adjust the height difference between each jacking point. By differentially controlling the lift at different jacking points, the bridge span gradually reaches the design required slope. Simultaneously, the cap beam is jacked up synchronously. Strict control is maintained over the stability of the jacking process to ensure the cap beam rises smoothly to the predetermined height, guaranteeing the stability and stress balance of the overall structure of the first span of the bridge.

[0050] S440: Remove the first longitudinal limiting device 14 at the eighth pier, then remove the third span of the bridge, and install the second lateral limiting device 15 at the end of the second span to limit the lateral displacement of the bridge. Install the second longitudinal limiting device 16 between the left and right spans of the bridge deck at the sixth pier to increase the safety guarantee during the overall synchronous jacking and stopping. Specifically, after completing the bridge jacking operation, the first longitudinal restraint device 14 at the eighth pier was removed, followed by the demolition of the third span of the bridge. During the demolition process, construction specifications must be strictly followed, the demolition sequence must be rationally planned, and the construction pace must be controlled to prevent structural imbalance or other safety hazards caused by the demolition work, ensuring the efficient and safe completion of the demolition work.

[0051] After the third span of the bridge is dismantled, a second lateral restraint device 15 needs to be installed at the end of the second span. The main function of this device is to effectively limit the lateral displacement of the bridge, providing lateral constraint for the bridge structure and ensuring the stability of the bridge during subsequent operations and use. Simultaneously, a second longitudinal restraint device 16 is installed between the left and right spans of the bridge deck at the sixth pier. This device further enhances the overall longitudinal restraint of the bridge, thereby increasing safety during the overall synchronous jacking phase and during periods of inactivity, ensuring that the bridge structure maintains good stability and safety under various working conditions.

[0052] Further, in step S440, the second lateral limiting device 15 adopts a frame-type lateral limiting, which includes multiple fifth steel pipe columns 1501, fifth lateral connecting rods 1502, fifth oblique connecting rods 1503, and second sliding rods 1504. The fifth steel pipe columns 1501 are fixed to the top of the reaction force embracing beam bearing platform by bolts. Multiple fifth lateral connecting rods 1502 and fifth oblique connecting rods 1503 are fixedly installed at intervals between the multiple fifth steel pipe columns 1501. A second sliding rod 1504 is slidably connected to each fifth steel pipe column 1501. The second sliding rod 1504 is fixedly connected to the bridge deck, and a stabilizing rod is fixedly installed between the second sliding rods 1504. The second longitudinal limiting device 16 includes a sixth steel pipe column 1601 and a third sliding rod 1602. The sixth steel pipe column 1601 is fixedly installed on the right bridge deck with bolts, and its bottom is leveled with mortar. Multiple transverse and diagonal connecting rods are installed between the sixth steel pipe columns 1601. Before installing the third sliding rod 1602, the pavement layer in the installation area of ​​the second longitudinal limiting device 16 needs to be removed. One end of the third sliding rod 1602 is slidably connected to the sixth steel pipe column 1601, and the other end is installed on the beam with anchor bolts. Multiple transverse and diagonal connecting rods are fixedly installed between the two third sliding rods 1602. During the installation process, care should be taken to avoid the top plate steel strands to prevent unnecessary impact on the structure.

[0053] S450: Lift the first and second spans of the bridge as a whole to the design elevation; Specifically, the first and second spans of the bridge were jacked up to the designed elevation using a control system. After the jacking was completed, the jacking support system was mechanically locked, i.e., the jacks were mechanically tightened, the pump station shut-off valve was closed, and the lateral connection welding of the support was completed.

[0054] S460: Install a sliding PTFE plate between the steel pipe support and the jack at the fourth pier. After installation, remove the first span of the abutment.

[0055] Specifically, during the period after the beam is lifted into position, the diurnal temperature variation can cause changes in the beam's length, which may adversely affect the underlying steel support structure. To address this issue, two sliding PTFE plates were installed between the jack cap and the steel pipe column at the fourth pier. This sliding between the beam and the bottom support effectively eliminates the stability problems caused by temperature differences, thereby ensuring the stability and safety of the entire structure.

[0056] For the demolition of abutment 1, a top-down, layered, and segmented approach was adopted. The volume of each segment after cutting should be controlled within 1 cubic meter to facilitate forklift handling. During the cutting process, water-drilled holes were used on the upper and lower layers of the segment to facilitate forklift arm access. The forklift arm then transported the segment off-site through these holes, thus completing the demolition work efficiently and safely.

[0057] S500: Extend the height of the first to eighth piers and transform abutment 1 into a pier structure; Specifically, the main steps involved in raising the bridge piers are as follows: Concrete removal: Before extending the column, remove 30cm of old pier concrete from the upper and lower surfaces of the pier column to form a "convex" joint surface and a 6mm rough surface, exposing the main reinforcement. After cleaning, use a cutting machine to trim the edge of the column to ensure that the edge is straight. Reinforcing bar processing and connection: Reinforcing bar processing is completed in the processing plant and inspected and accepted after being transported to the site. The main bars are mechanically connected, and the joint standard is Grade I. They are staggered. Within the joint section, the hoops are spot welded to the main bars. When binding the reinforcing cage, ensure that the grade, diameter, number and spacing of the reinforcing bars meet the design requirements. The bound or welded reinforcing mesh and reinforcing cage shall not be deformed, loose or unwelded. Steel formwork installation: After the steel formwork is processed off-site, it is transported to the construction site. When assembling the formwork, double-sided tape is used at the joints to prevent grout leakage. After assembly, the joints are cleaned and water-based release agent is applied. After the formwork is installed, guy ropes are used to secure it. The plane position and verticality of the formwork are re-measured to ensure installation accuracy. The top of the formwork is higher than the top surface of the connecting column, and hoppers are symmetrically opened to facilitate concrete pouring and vibration. Concrete pouring: Before pouring concrete, check the formwork, reinforcement and protective layer. Use self-compacting C40 concrete and pour it in one go. Use a wall-mounted vibrator to compact the concrete to ensure it is dense. The top surface is constructed from the gap between the pier top and the beam bottom. When the concrete strength reaches 50% of the design strength, the formwork can be removed. After demolding, wrap it with plastic film for curing for no less than 7 days.

[0058] S600: Remove the existing pad stone on the top of the cap beam, retain the pad stone reinforcement and arrange the steel mesh according to the drawing, erect the formwork and pour the concrete. After the concrete strength reaches the standard, the beam is lowered simultaneously. After all the bearing pad stones are replaced, the bridge deck paving and ancillary works can be constructed. Specifically, it mainly includes the following steps: Stone removal: The upper stone is removed using an electric pneumatic hammer. Excess stone height and style are removed according to the design drawings. After the concrete of the stone is removed, the reinforcing steel is retained, and a steel mesh is laid according to the design drawings.

[0059] Foundation stone pouring: The foundation stone is removed, and the erected formwork is flush with the top of the support. The foundation stone is poured in one go to ensure a tight fit between the foundation stone and the support. The foundation stone is reinforced with steel bars according to the design drawings, and C60 self-leveling mortar is used.

[0060] After the reinforcement mesh of the pad stone is added, the upper pad stone is constructed using the suspended formwork method, similar to the construction of the leveling blocks under the cap beam in the first jacking of the temporary support system. φ12mm suspension rod bolts are welded to the existing pad stone reinforcement at the bottom of the box girder. Five suspension rods are welded around the four corners and the middle of the pad stone. Then, the bottom formwork of the lower pad stone steel plate is suspended on the hooks, leveled, and then the side formwork is installed around it. The side formwork is assembled from bamboo plywood, with internal dimensions consistent with the pad stone dimensions. Grouting holes and grout outlet holes are pre-reserved at the top of the side formwork.

[0061] C60 self-leveling mortar was used for the pouring of the upper pad stone. The C60 mortar was pressed into the template by a grouting pump. The grout flowing out of the grout outlet is considered as the upper pad stone being poured fully. The grouting process was carried out slowly.

[0062] Lowering the beam: After the strength of the upper pad stone reaches the design requirements, check that the oil circuit and electrical circuit are connected normally and that the hydraulic equipment is operating normally, then start depressurizing and lowering the beam synchronously with the jacks (after the jacks are lifted to the position, the mechanical screws are tightened and the oil cylinders maintain pressure. In this state, the jack extension is <3cm and the beam lowering height is small). The principle of lowering the beam is that the oil cylinder returns oil and retracts, and the procedure is the opposite of the lifting process.

[0063] After the beam is lowered into place, the upper bearing pad and the new bearing are inspected. If any gaps are found or the contact is not tight, ultra-thin steel plates are used to fill them. After all the bearing pads have been replaced, the bridge deck paving and ancillary works can be carried out.

[0064] S700: Repeat steps S100 to S600 to carry out jacking construction on the left side of the bridge; Specifically, repeat steps S100 to S600 above to lift the left span of the bridge until the adjustment of the left span of the bridge and the construction of the bridge deck paving and ancillary works are completed, that is, the bridge adjustment is completed.

[0065] S800: Lifting equipment materials dismantling and removal from the site.

[0066] Specifically, after the bridge is lifted into place, the columns are heightened, and the abutments are transformed into a pier + cap beam configuration, the concrete strength of each pour reaches 100%, and the cap beam is tensioned and grouted. Then, a hand hoist is used to fix the steel crossbeam to the lifting point on the box girder during installation.

[0067] Jack Removal: The jack control system slowly depressurizes the jacks, transferring the load on the bridge structure from temporary supports to the columns and cap beams. After depressurization, remove the steel plates used to fill the gap between the jacks and the steel supports, or disconnect the bolts connecting the 0.1m and 0.2m adjusting steel pipes to the lower steel supports. Use a hand hoist to pull out the adjusting steel pipes and place them on the ground. Then, use a hand hoist to secure the jacks to the steel crossbeam, disconnect the bolts between the jacks and the crossbeam, detach the jacks from the crossbeam, and use a hand hoist to pull the jacks outside the steel supports. Finally, slowly lower the jacks to the ground.

[0068] Steel distribution beam removal: Fix the steel distribution beam to the box girder with a hand chain hoist, then use an oxy-fuel cutting device to separate the steel distribution beam from the welded position of the bottom steel plate of the leveling pad, so that the steel distribution beam is detached from the leveling pad. Use a hand chain hoist to pull the steel distribution beam out above the steel support, and then slowly lower it to the ground. Use a truck crane to lift and transport the steel distribution beam away.

[0069] Removal of leveling blocks: The concrete is removed by electric pneumatic hammer, and the embedded steel bars are cut with a grinding wheel cutter. The cut is made inside the concrete surface of the cap beam. Then, cement-based waterproof coating is applied to the area of ​​the leveling blocks, with the color matching the concrete.

[0070] Steel support dismantling: Similar to installation, steel support dismantling begins with detaching the horizontal couplings in the temporary support system. Using jacks and a truck crane, the couplings are cut off and transported to the material storage area for dismantling, sorting, and stacking. Then, the steel supports are dismantled row by row and piece by piece. Using a hand-operated hoist and truck crane, the steel supports are lifted and pulled out of the beam's projection area. A crane then lowers each steel support to the ground and lays it down. Transport vehicles then transport the relevant materials to the material storage area, where they are neatly sorted and stacked.

[0071] Furthermore, before the bridge is jacked up, elevation observation points are set up on the bridge deck, settlement monitoring points are set up on the reaction column beam abutment, vertical displacement monitoring points are set up on the main beam and cap beam, longitudinal displacement monitoring points are set up at the expansion joint, stress monitoring points are set up on the main beam, steel pipe column and cap beam, and temperature monitoring points are set up on the main beam.

[0072] Bridge deck elevation monitoring: Three elevation observation points are set up on the bridge deck at each pier top section. One measuring line is set up at each end of the bridge deck and the center line of the bridge deck at the upstream and downstream ends of each precast continuous box girder. The pre-embedded measuring points on the bridge deck are made by inserting φ20 steel bars into the top of the box girder and extending about 3cm out of the bridge deck. The measuring instrument is a total station. The method of fixing the prism by drilling holes in the top of the guardrail and installing expansion bolts is adopted. Initial data is measured once before jacking and once a day during jacking.

[0073] Settlement monitoring of the reaction-supported column-supported pier cap: Two foundation settlement monitoring points are set up on the outer side of each pier's column-supported pier. The elevation of the foundation settlement monitoring points is measured using a precision level. Initial data is measured once before jacking and once a day during the jacking process.

[0074] Vertical displacement monitoring of the bridge beam: One point is set up at each of the upstream and downstream ends of the bridge. A pull-wire displacement meter is installed at the designated measuring point. The displacement meter is connected to the data acquisition instrument via a data cable. The data acquisition instrument transmits the data to the cloud platform via a 4G network. Data is collected in real time during the jacking process, with a collection frequency of 1 time / minute.

[0075] Vertical displacement monitoring of the cap beam: One point is set on each side of the bottom of the cap beam. A wire displacement gauge is installed at the designated measuring point. The displacement gauge is connected to the data acquisition instrument via a data cable. The data acquisition instrument transmits the data to the cloud platform via a 4G network. Data is collected in real time during the jacking process, with a collection frequency of 1 time / minute.

[0076] Longitudinal displacement monitoring of the bridge beam: At the expansion joints on the top surfaces of the fourth and eighth piers, one measuring point is set up at each of the upstream and downstream ends of the bridge, spanning the expansion joints and perpendicular to them. A pull-wire displacement gauge is installed at each of the designated measuring points. The gauge is connected to a data acquisition device via a data cable. The data acquisition device transmits data to a cloud platform via a 4G network. Data is collected in real time during the jacking process, at a frequency of once per minute.

[0077] Stress monitoring of main beam: Stress test sections are arranged on the box girder, selected at the negative bending moment zone section near the support of each span and the mid-span section. In addition, the changes of the original cracks in the beam during the jacking process are monitored by selecting a representative transverse crack at the mid-span and installing a crack sensor with a range of 5mm and a sensitivity of 6.3×10-6mm / Hz2.

[0078] Stress monitoring of the cap beam: Stress monitoring points are set at the root of the flange plate of the cap beam.

[0079] Stress detection of steel supports: Vibrating wire strain gauges are also used on the bottom surfaces of the steel supports symmetrically arranged on both sides of the pier to monitor the stress and deformation of the steel supports and determine the stability of the steel supports. The jacking process is monitored in real time, and the sampling frequency of displacement and stress monitoring data is 1Hz.

[0080] Main girder temperature monitoring: Three observation sections were set up at the bottom of the box girder at the mid-span section in the longitudinal direction of half of the bridge, and temperature sensors were attached to the bottom of the box girder. Temperature monitoring of the bridge structure was carried out to obtain the atmospheric temperature corresponding to stress and displacement, thereby providing technical parameters for mechanical analysis and construction control analysis.

[0081] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for adjusting the slope and lifting the jacking mechanism of a multi-section, initially simply supported, then continuously skewed small box girder, characterized in that... Includes the following steps: S100: First, remove the bridge crash barriers, pedestrian guardrails, expansion joints, and bridge drainage system of the first and second sections on the right side. S200: Excavate the earthwork at the bridge abutment (1) and the first to eighth piers (2-9), pour the cushion layer, construct the reaction foundation corbel at the bridge abutment (1) and the reaction column beam foundation at the first to eighth piers (2-9), and set up a first jacking support system (10) on the top of the reaction foundation corbel, and set up a second jacking support system (11) and a third jacking support system (12) on the top of the reaction column beam foundation. S300: Install a first lateral limiting device (13) at the end of the abutment (1), and install several first longitudinal limiting devices (14) on the top of the bridge deck of the fourth pier (5) and the eighth pier (9). S400: Lift the main beams and cap beams of the first and second sections respectively; S500: The first to eighth piers (2-9) will be extended and the abutment (1) will be transformed into a pier structure; S600: Remove the existing pad stone on the top of the cap beam, retain the pad stone reinforcement and arrange the steel mesh according to the drawing, erect the formwork and pour the concrete. After the concrete strength reaches the standard, the beam is lowered simultaneously. After all the bearing pad stones are replaced, the bridge deck paving and ancillary works can be constructed. S700: Repeat steps S100 to S600 to carry out jacking construction on the left side of the bridge; S800: Lifting equipment materials dismantling and removal from the site.

2. The method for adjusting the slope and lifting the overall structure of a multi-section, initially simply supported, then continuous, oblique small box girder according to claim 1, is characterized in that... In step S200, when constructing the reaction foundation corbel at the bridge abutment (1), firstly, mechanical excavation is carried out on both sides of the cross section, then layered slope excavation is carried out on the part under the bridge, and formwork is erected according to the design dimensions of the reaction foundation corbel, and roughening is carried out at the interface between the new and old concrete, then steel bars are inserted into the bridge abutment pier, and steel bars are tied in the formwork according to the design requirements, and finally the reaction foundation corbel is poured. When constructing the reaction column abutments at the first to eighth piers (2-9), the foundation is excavated in layers with slope according to the design dimensions of the reaction column abutments. Formwork is erected, and the interface between the old and new concrete is roughened. Reinforcing bars are inserted into the pier columns and tied in the formwork according to the design. Then the reaction column abutments are poured.

3. The method for adjusting the slope and lifting the overall skewed small box girder of multiple sections, initially simply supported and then continuously skewed, as described in claim 2, is characterized in that... In step S200, the first lifting support system 10 includes a first steel pipe column (1001), a first transverse connecting rod (1002), a first inclined connecting rod (1003), a first jack (1004), and a first steel distribution beam (1005). Each reaction foundation bracket has multiple first steel pipe columns (1001) fixedly installed on its top by bolts. The multiple first steel pipe columns (1001) are distributed in a triangular pattern. Multiple first transverse connecting rods (1002) and first inclined connecting rods (1003) are spaced apart between every two first steel pipe columns (1001). The top of the first steel pipe column (1001) is provided with four inverted first jacks (1004). The top of the four inverted first jacks (1004) is fixedly installed with a first steel distribution beam (1005) by bolts. The first steel distribution beam (1005) is located at the bottom of the main beam. The second jacking support system 11 is installed on the top of the reaction column-supporting beam abutment of the first to seventh piers (2-8). It includes a second steel pipe column (1101), a second transverse connecting rod (1102), a second oblique connecting rod (1103), a second jack (1104), a third jack (1105), and a second steel distribution beam (1106). Multiple second steel pipe columns (1101) are bolted to the top of each reaction foundation corbel. The multiple second steel pipe columns (1101) are symmetrically arranged in the transverse and longitudinal directions of the pier. Every two first steel pipe columns (1101) 01) Multiple second transverse connecting rods (1102) and second oblique connecting rods (1103) are provided at intervals between them. Four second jacks (1104) are installed on the top of the second steel pipe column (1101) at the bottom of the cap beam. The second jacks (1104) are located at the bottom of the cap beam. An inverted third jack (1105) is installed on the top of the second steel pipe column (1101) on each side of the pier cap beam. The top of the inverted third jack (1105) is fixed with a second steel distribution beam (1106) by bolts. The second steel distribution beam (1106) is located at the bottom of the main beam. The third jacking support system (12) includes a third steel pipe column (1201), a third transverse connecting rod (1202), a third inclined connecting rod (1203), a fourth jack (1204), a fifth jack (1205), and a third steel distribution beam (1206). Multiple third steel pipe columns (1201) are bolted to the top of each reaction foundation corbel. Multiple second steel pipe columns (1201) are symmetrically arranged along the longitudinal direction of the bridge pier. Multiple third transverse connecting rods are spaced apart between every two first steel pipe columns (1201). The connecting rod (1202) and the third inclined connecting rod (1203) are connected by four fourth jacks (1204) installed on the top of the third steel pipe column (1201) at the bottom of the cap beam. The fourth jacks (1204) are located at the bottom of the cap beam. An inverted fifth jack (1205) is installed on the top of the second steel pipe column (1201) on the left side of the cap beam of the eighth pier (9). The inverted fifth jack (1205) is fixed to the top of the third steel distribution beam (1206) by bolts. The third steel distribution beam (1206) is located at the bottom of the main beam.

4. The method for adjusting the slope and lifting the overall sloping section of a multi-section, initially simply supported, then continuously skewed small box girder according to claim 1, characterized in that... In step S300, the first lateral limiting device (13) adopts a frame-type lateral limiting, which includes multiple fourth steel pipe columns (1301), fourth lateral connecting rods (1302), fourth oblique connecting rods (1303) and first sliding rods (1304). The fourth steel pipe columns (1301) are fixed to the top of the bridge abutment by bolts. Multiple fourth lateral connecting rods (1302) and fourth oblique connecting rods (1303) are fixedly installed at intervals between the multiple fourth steel pipe columns (1301). A first sliding rod (1304) is slidably connected to each fourth steel pipe column (1301). The first sliding rod (1304) is fixedly connected to the bridge deck, and a stabilizing rod is fixedly installed between the first sliding rods (1304). The first longitudinal limiting device (14) is a boat-shaped longitudinal limiting device, which includes a reaction frame (1401), a pull plate (1402), a transverse diaphragm (1403), a screw jack (1404), a pad (1405), and a reaction plate (1406). The pull plate (1402) is fixedly installed between its ends, the transverse diaphragm (1402) is fixedly installed between its middle parts, and the other end is fixedly installed between its ends. The reaction plate (1406) is fixedly installed with a pad (1406) facing inward. The pad (1405) and the transverse diaphragm (1402) are provided with a screw jack (1404). The first longitudinal limiting device (14) is fixedly connected to the bridge deck at the expansion joint of the fourth pier (5) and the eighth pier (9) through the transverse diaphragm (1402) and the reaction frame (1401) respectively, thereby limiting the longitudinal displacement of the bridge.

5. The method for adjusting the slope and lifting the overall structure of a multi-section, initially simply supported, then continuous, oblique small box girder according to claim 1, characterized in that... Step S400 specifically includes the following steps: S410: Lift the first section of the bridge as a whole to ensure that all parts within the section rise synchronously. At the same time, carry out slope adjustment and lifting operations for the second section. By precisely controlling the height difference of each lifting point, the bridge section can achieve the slope required by the design. S420: According to the cutting position determined by the construction drawings, the first to seventh piers (2 to 8) are cut. After the cutting is completed, the cap beam is lifted. The cap beam is lifted steadily to the predetermined height by gradually lifting with jacks. S430: The first section of the bridge is jacked up to adjust the slope. By precisely controlling the height difference of each jacking point, the section of the bridge reaches the slope required by the design. The cap beam is then jacked up synchronously, so that the cap beam rises smoothly to the predetermined height. S440: Remove the first longitudinal limiting device (14) at the eighth pier (9), then remove the third bridge section, and set a second lateral limiting device (15) at the end of the second section to limit the lateral displacement of the bridge. Set a second longitudinal limiting device (16) between the left and right bridge decks at the sixth pier (7). S450: Lift the first and second spans of the bridge as a whole to the design elevation; S460: Install a sliding PTFE plate between the steel pipe support and the jack at the fourth pier (5). After installation, remove the first span of the bridge abutment (1).

6. The method for adjusting the slope and lifting the overall structure of a multi-section, initially simply supported, then continuous, oblique small box girder according to claim 5, is characterized in that... When jacking the first and second sections of the bridge, an alternating cyclic jacking method using two sets of jacks is adopted. While one set of jacks is depressurized, the other set of jacks is already under support. The jacking process is as follows: Before the formal jacking, a trial jacking should be carried out. The trial jacking height is 10mm. The working performance of the jacks and temporary support system and the stability of the box girder are checked during and after the jacking process. The cap beam can only be jacked after the pier columns are cut according to the design requirements. The jacking speed is controlled at 1-3mm / min. The weight of the jacking section structure is calculated by using the jacking pressure and jack parameters and compared with the design weight. After the trial jacking is completed, if there are no problems, the formal jacking will begin. Each jacking stroke is 100mm, and the maximum jacking speed is 3mm / min. The jacking support system is synchronously controlled by the PLC hydraulic control system to achieve synchronous slope adjustment and jacking of the bridge. During the jacking process, the jacks are shimmed in stages. The jacks are first shimmed with 1cm steel plates according to the jacking height, and then replaced with 0.1m, 0.2m, 0.5m, 1m, and 2m steel supports in sequence. The longitudinal and transverse connecting rods are immediately added to enhance the stability of the support.

7. The method for adjusting the slope and lifting the overall structure of a multi-section, initially simply supported, then continuous, oblique small box girder according to claim 5, is characterized in that... In step S440, the second lateral limiting device (15) adopts a frame-type lateral limiting, which includes multiple fifth steel pipe columns (1501), fifth lateral connecting rods (1502), fifth oblique connecting rods (1503), and second sliding rods (1504). The fifth steel pipe columns (1501) are fixed to the top of the reaction force column beam support by bolts. Multiple fifth lateral connecting rods (1502) and fifth oblique connecting rods (1503) are fixedly installed at intervals between the multiple fifth steel pipe columns (1501). A second sliding rod (1504) is slidably connected to each fifth steel pipe column (1501). The second sliding rod (1504) is fixedly connected to the bridge deck, and a stabilizing rod is fixedly installed between the second sliding rods (1504). The second longitudinal limiting device (16) includes a sixth steel pipe column (1601) and a third sliding rod (1602). The sixth steel pipe column (1601) is fixedly installed on the right bridge deck by bolts, and its bottom is leveled with mortar. The sixth steel pipe columns (1601) are connected by multiple transverse and diagonal connecting rods. Before installing the third sliding rod (1602), the pavement layer in the installation area of ​​the second longitudinal limiting device (16) needs to be removed. One end of the third sliding rod (1602) is slidably connected to the sixth steel pipe column (1601), and the other end is installed on the beam by anchor bolts. Multiple transverse and diagonal connecting rods are fixedly installed between the two third sliding rods (1602). During the installation process, care should be taken to avoid the top plate steel strands to prevent unnecessary impact on the structure.

8. The method for adjusting the slope and lifting the overall sloping section of a multi-section, initially simply supported, then continuously skewed small box girder according to claim 1, characterized in that... In step S500, the main steps included during the extension construction of the bridge piers are as follows: Concrete removal: Before extending the column, remove 30cm of the old pier concrete from the upper and lower surfaces of the pier column to form a "convex" joint surface and a 6mm rough surface, exposing the main reinforcement. After cleaning, use a cutting machine to trim the edge of the column to ensure that the edge is straight. Reinforcing bar processing and connection: Reinforcing bar processing is completed in the processing plant and inspected and accepted after being transported to the site. The main bars are mechanically connected, and the joint standard is Grade I. They are staggered. Within the joint section, the hoops are spot welded to the main bars. When binding the reinforcing cage, ensure that the grade, diameter, number and spacing of the reinforcing bars meet the design requirements. The bound or welded reinforcing mesh and reinforcing cage shall not be deformed, loose or unwelded. Steel formwork installation: After the steel formwork is processed off-site, it is transported to the construction site. When assembling the formwork, double-sided tape is used at the joints to prevent grout leakage. After assembly, the joints are cleaned and water-based release agent is applied. After the formwork is installed, guy ropes are used to secure it. The plane position and verticality of the formwork are re-measured to ensure installation accuracy. The top of the formwork is higher than the top surface of the connecting column, and hoppers are symmetrically opened to facilitate concrete pouring and vibration. Concrete pouring: Before pouring concrete, check the formwork, reinforcement and protective layer. Use self-compacting C40 concrete and pour it in one go. Use a wall-mounted vibrator to compact the concrete to ensure it is dense. The top surface is constructed from the gap between the pier top and the beam bottom. When the concrete strength reaches 50% of the design strength, the formwork can be removed. After demolding, wrap it with plastic film for curing for no less than 7 days.

9. A method for adjusting the slope and lifting the overall structure of a multi-section, initially simply supported, then continuously skewed small box girder according to any one of claims 1-8, characterized in that... Before the bridge is jacked up, elevation observation points are set up on the bridge deck, settlement monitoring points are set up on the reaction column bearing platform, vertical displacement monitoring points are set up on the main beam and cap beam, longitudinal displacement monitoring points are set up at the expansion joint, stress monitoring points are set up on the main beam, steel pipe column and cap beam, and temperature monitoring points are set up on the main beam.

10. A method for adjusting the slope and lifting the overall structure of a multi-section, initially simply supported, then continuously skewed small box girder according to any one of claims 1-8, characterized in that... During the jacking process, wedge-shaped steel plates are inserted between the steel distribution beam and the jacks to adjust the verticality of the jacks. With the help of the bolt return holes, the jacks can move back and forth in the direction of the bridge, thereby eliminating deviations and avoiding the influence of beam rotation.

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